1. Field of the Invention
The present invention relates to a technique of obtaining the position and orientation of a target object.
2. Description of the Related Art
Along with the recent development of robot technologies, robots are replacing humans to do complex tasks such as assembly of industrial products, which have been done by humans. A robot picks parts using an end effector such as a hand, and assembles them. Conventionally, parts to be picked are supplied using an apparatus called a parts feeder for supplying parts one by one in line, or supplied by heaping parts in various orientations in a pallet (box). When the parts feeder is used, each part is supplied in a predetermined position and orientation, and the robot relatively easily picks it. However, it additionally costs to prepare the parts feeder. In some cases, different parts feeders need to be prepared in accordance with the shapes of parts. In contrast, heaping and supplying parts can avoid an increase in cost because parts are only placed in the pallet. Following a recent trend toward high-mix low-volume production, attention is paid to heaped supply capable of quickly coping with various parts.
In a conventional technique disclosed in Japanese Patent No. 04226623, if extraction or gripping of a part by a robot from a heap fails, the target part is excluded from gripping targets by a predetermined number of times. Excluding the part failed in extraction or gripping by a predetermined number of times can avoid a repetitive failure for a while.
However, the method disclosed in Japanese Patent No. 04226623 passively waits for a change of the positions and orientations of parts by excluding a part failed in extraction by the robot from gripping targets by a predetermined number of times. In this method, the number of gripping target candidates decreases while work is done by a predetermined number of times. Since the number of heaped parts is limited, work cannot be performed efficiently if the number of candidates decreases.